I've got a few Pentax lenses that test poorly yet produce nice images so it's not always about ultimate corner-to-corner sharpness and low CA.Still, however good this new 58mm is, I'll be hard pressed to buy it to get just a little more something from it over my old 50/1.4. UNLESS I actually need it for night photography where I need the pinpoint lights to look as crisp as they should.